The present invention relates to a vibration testing apparatus and, more particularly, to a vibration testing apparatus arranged to provide vibration in multiple axes.
It is well known to test articles under simulated use conditions, such as simulations of vibrational forces to which the articles are likely to be exposed. This type of testing is performed for articles such as engine parts, wrist watches, and electronic components, such as cameras and mobile phones. For purposes of illustration, the present invention will be described primarily in connection with its application to vibration testing of mobile phones, but it will be understood that the present invention is equally applicable to testing of other articles.
Vibration testing of articles such as mobile phones will typically attempt to simulate what is expected to happen to the article over long periods of use. Presently available methods vibrate the mobile phones in one direction at a time. Unfortunately, this type of vibration is not characteristic of the vibration to which the phone will actually be exposed during actual use. Comparisons of scratch patterns on laboratory tested phones with those of phones used in the field revealed that the laboratory tested phones have various linear scratches, whereas the phones that were actually used tend to have more blurred scratches reflecting vibration in multiple axes.
Various vibration test apparatus are known, many of which vibrate in multiple axes. For example, U.S. Pat. No. 4,875,374 discloses a test apparatus with a plurality of actuator arms connected to respective drive shafts. U.S. Pat. No. 3,691,822 discloses an apparatus that provides for vibration in three orthogonal directions, with a main object of the vibrator being to maintain a level or horizontal orientation of the object under test. U.S. Pat. No. 4,436,188 discloses a controlled motion apparatus capable of several degrees of freedom that uses three anti-rotating actuators. U.S. Pat. No. 5,650,569 discloses a skewed, multi-axis vibration fixture where a skewed angle between the device under test and the vibration axis is invariable.
In devices to be vibration tested, particularly mobile phones, it is often desirable to provide vibration in all degrees of freedom, translation and rotation. Other characteristics of the test device preferably include:
substantially equal vibration over the entire test surface or rig such that multiple devices on the surface or rig will have been exposed to the same load;
equal vibration over time to minimize problems of repeatability;
minimal size so that the test apparatus can fit inside or under a climate controlled test chamber with limited volume;
ability to generate vibrations in all six degrees of freedom (three translation, three rotation), although not necessarily equal vibrations in all directions;
ability to operate at any frequency range;
frequency range between 5-5000 Hz, preferably at least around 10-500 Hz. Vibration is preferably random, and not a sinusoidal oscillation. The Acceleration Spectral Density (ASD) is not limited but is preferably lower at high frequencies;
ability to mount multiple articles for test on a single fixture;
accessible system and antenna outlets during test for measurement purposes;
ability to withstand a predefined environment, such as at least 70xc2x0 C. and 93% relative humidity;
ability to perform tests without handling of articles being tested.
In accordance with one aspect of the present invention, a vibration testing apparatus is arranged to provide vibration in multiple axes and includes a first frame member, at least one actuator connected to the first frame member for vibrating the first frame member in a first direction, and a second frame member for holding devices under test, the second frame member having an axis and being connected to and arranged to vibrate with the first frame member and being arranged to turn about the axis relative to the first frame member.
In accordance with another aspect of the present invention, a method of vibration testing includes mounting at least one device to be tested on a test frame, turning the test frame about an axis relative to a main frame, and vibrating the main frame in a first direction.
In accordance with yet another aspect of the present invention, a method of setting up a multiple axis vibration testing apparatus includes selecting an angle through which a test frame of the testing apparatus is adapted to turn about an axis thereof relative to the main frame, the test frame being adapted to have at least one device to be vibration tested mounted thereon, and positioning the test frame at a non-zero angle relative to the main frame selected as a function of the angle.